Realistic simulation of the neck response in a dummy is of vital importance to obtain a humanlike dynamical behavior of the head. Trajectories of the head and the nature of head contact with vehicle interior or exterior are critically dependent on the dummy's neck design.Neck performance criteria in literature are limited to the neck response in forward flexion and extension. Recent research programs to develop dummies with omnidirectional biofidelity clearly show a need for additional requirements in lateral and oblique directions. In this study, dynamic lateral flexion tests with human volunteers conducted by the Naval Biodynamics Laboratory (NBDL) in New Orleans are analysed.It follows that the observed head neck motions in this type of impact quite well can be represented by a system with three degrees of freedom: a head and neck rotation in the plane of impact and a head torsion about the head anatomical z-axis. Mechanical and geometrical properties of this system resulting from tests with 6 different subjects under various test conditions are presented.Based on this analysis, a simple test set-up is proposed, derived from the most severe NBDL test conditions, for the evaluation of existing or future mechanical head-neck designs. Requirements for the head motion in this specific test set-up are presented.